Trojans will never look at weather maps in quite the same way. Whether watching Fox-TV in Burbank, or CNN in Beijing, theyll know that the highs and lows shown for downtown Los Angeles really reflect climate conditions at USC  about 50 feet west of the David X. Marks Tennis Stadium, to be precise.Thats the site of the National Weather Services new downtown weather station. In June, the federal agency commissioned a state-of-the-art AutomatedSurface Observing System (ASOS) at USC. The ASOS network provides more accurate, uniform and frequent weather updates. About 900 such stations exist nationally.The new array at USC replaces sensors that have operated on the roof of the Department of Water and Power building since 1987.The more accurate weather measurement is on the ground because people live on the ground, says Gary Ryan, a meteorologist at the National Weather Service.Gone too are the familiar NWS references to weather conditions at the "Los Angeles Civic Center."The new descriptor is "Downtown Los Angeles at USC."